Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
A number of scientific methods have been developed in the medical field to evaluate a person's health state. A person's health state may, for example, be evaluated based on the measurement of one or more physiometric parameters, such as pulse, oxygen saturation (SpO2), and blood pressure. In a typical scenario, these measurements may be taken in the home or a health-care setting by using several discrete devices or sensors and, in some cases, by drawing blood or other bodily fluid. For most people, the measurements or blood tests are performed infrequently, and changes in a physiometric parameter, which may be relevant to health state, may not be identified, if at all, until the next measurement is performed.
Monitoring of an individual's circadian cycle may also be important to evaluating health state. The timing of many molecular, behavioral, mental and physical functions is governed by one or more circadian rhythms. Circadian rhythms can be used in the diagnosis sleep disorders, intervene on abnormal sleep patterns, time the delivery of therapeutic agents, optimize activity and performance, and modify behavior. Indications of the circadian cycle may include an individual's sleep/wake, appetite, thirst, excretion, core body temperature and physical activity cycles.
The timing of a mammal's circadian rhythm is typically measured by phase markers such as melatonin secretion, core body temperature and plasma level of cortisol. At present, these markers are measured infrequently, for example, when an individual visits a physician or laboratory, or at certain points throughout the day. Further, cortisol level and melatonin secretion are generally measured by invasive procedures, such as a blood draw. Other modes of gathering information regarding an individual's circadian cycle, such as actigraphy and questionnaires can suffer from a lack of sensitivity and reliability.